As the W3C points out, XHTML 2.0 is a relative of the Web’s familiar publishing languages, HTML 4 and XHTML 1.0 and 1.1, and is not intended to be backward compatible with them. That is, XHTML 2.0 is not the “latest and greatest” upgrade to earlier markup languages, making them obsolete; rather, it is meant to be seen as a new member in the family of markup languages available for Web builders to choose from.